Method of weighting silk



Patented July 17, 1934 1,966,991 METHOD OF WEIGHTING SILK Frederick Miller, Beileville, N. J., assignor to Harold E. Kampf, New York, N. Y., and David L. Cole, Paterson, N. J. I

No Drawing Application June 13, 1932, Serial No. 617,056

1 Claim.

This .invention relates to the art of weighting natural silk.

In the trade, weighting is the term used to denote the addition of weight other than the weight of the silk. This weighting is accomplished by anchoring to the fiber, some metallic compound or mixture which-is, as-near as possible, in an inert state with respect to the properties of the goods, factory operation, and merchandising requirements.

There is a theoretical amount of weighting about 150% over par, beyond which there is no utility recognized by the trade. But heretofore, no one to the best of my knowledge has been successful in obtaining this amount without sacriiicing many of the qualities of the silk.

In the prior art, will be found processes that obtain this weighting by use of metallic compounds such as iron, tin, aluminum, silicon, etc., but the best results obtained from these were around above par. Par is usedhere to designate the weight of the-silk in the raw condition. There is also found in the prior art and practiced in the trade a weighting process that uti lizes a lead compound. While this lead compound weighting is a very marked advance in the amount of-weight taken up by the'silk, nevertheless, some of the characteristics of the silk are sacrificed.

One of the features of the silk that is sacriflood is that the fiber of the silk is distorted to a flat strand giving a dead appearance to the silk fabric from having been flattened or compressed. In 'my invention, the fiber of the silk is slightly swollen imparting the silky touch and lovely appearance which is the recognized characteristic of silk.

Another objection to the weighting with lead compounds'arises in discharge printing that subsequently follows the weighting operation. It is well recognized that a silk weighted with lead compounds will not yield a white discharge. A grey color is the nearest approach to white, and the grey color is due to the fact that there is always .a residual deposit of lead sulphide remainingin' the silk. In my invention I obtain a clear white or natural silk colored discharge with standard discharge methods.

Being able to discharge colors to white or natural silk color is of paramount importance to the manufacturer. The fastidious public demand various colors and the demand will decline intermittently leaving the manufacturer with a stock of piece goods without a market for it. To be able to discharge these colors and print them into readily saleable stock of popular color is an adjunct of the features above enumerated.

In its broadest aspect my invention comprehends a step or steps in the process of weighting natural silk which involves the use of a soluble zinc salt for overcoming the foregoing shortcomings pointed out in connection with the use of lead compounds. Any of the water-soluble zinc salts will operate equally well in the particular step or steps enumerated hereinafter; but it has been found that the most successful yields result from the use of zincacetate ZI1(C2H3O2)2. Furthermore, I have found that zinc acetate will give substantially the same amountofweight as the lead compounds when used alone, as will be understood from the detailed description, (Operations A and B) when it is desired to elimi nate the use of lead compounds entirely. It has alsobeen found that the initial weighting with the tin compounds of the prior art may be dis pensed with by substituting therefor sodium zincate or zinc acetate. It is necessary however, in this latter event to use lead acetate in conjunction with the zinc acetate. (See Operation A-l) Operation A Step '1. In carrying out the invention, the fiber, skein or fabric of natural silk is subjected to a de-gumming bath. In common practice this amounts to boiling the silk material in an olive oil soap bath. Step 2 consists of thereafter washing thoroughly in successive operations in hot and cold water slightly acidified toa 1% solution of hydrochloric acid, the excess acid being removed by another washing operation in cold water. Step 3 consists of subjecting the degummed, washed material to "immersion in stannic chloride lQ" to 25 Baum for approximately one hour. Step 4 consists of removing excess stannic chloride by centrifugal force, or anyrother method, and thereafter soaking the fabric in cold water to hydrolize the stannic chloride remaining in the fiber. The result of the hydrolysis leaves tin hydrate and hydrochloric acid and the hydrochloric acid is held in the liquid (water) with the tinfhydrate on the silk. Care must be taken to have enough water in'the b th to remove all free hydrochloric acid. Step 5. Thereafter the material is subjected to a solution of di-sodium phosphate at approximately 145 F. and approximately 5 Baum. In treating the silk with di-sodium phosphate it is immersed for about twenty minutes. Excess di-sodium phosphate is then removed by washing with hot water at 145 F. and then again washing with a 1% solution of hydrochloric acid in cold water. At this point tin phosphate has formed on the silk. Step 6. For this step in Operation A, the steps, 3, 4 and 5 are repeated, three or more times, the final product increasing in weight in proportion to the number of passes made.

Operation A-I The silk is immersed in a solution of sodium zincate for 40 minutes. After removing the excess solution, the silk is then subjected to a solution of a soluble lead compound (such as lead acetate or lead nitrate), of 3 Baum strength at a temperature of 135 F. and for approximately 40 minutes. The silk is then thoroughly washed in cold water, then hot water, and again in cold water. This will complete the formation of lead zincate. The reaction takes place as follows:

To add additional weight and fix the same on the silk, it is passed through a cold 2% solution of di-sodium phosphate, thus forming leadzinc-phosphate. In case still more weight or other characteristics shall be desired, the silk may then be subjected to Operation D, described later.

Operation B At this point in the process my invention deviates from the prior art, the general procedure thereof being as described in the title Operation A. It will therefore be understood that Operation A will be considered as a preliminary step or steps to the invention which is claimed as mine.

Step 1 B. After the steps of Operation A have been completed, the material is treated with an acetic acid wash for approximately twenty minutes. The acetic acid solution is preferably 2 Baum, and at a temperature of 150 F. Step 2 B. Then the silk is treated for about forty-five minutes in a 5 Baum solution of the zinc acetate after which it is:

Step 3 B. Rinsed in a cold, hot, and then a cold bath of water successively. Step 4 B. The silk is then immersed in a 3 Baum solution of cold di-sodium phosphate for about twentyfive minutes, and;

Step 5 B then rinsed in hot and cold water successively. Step 6 B. By repeating steps 2, 3, 4 and 5 of Operation B additional weight may be incorporated in the silk up to 140 percent above par.

At this point in the process the zinc acetate is converted into an insoluble zinc salt (zinc -stannophosphate) which is a definite chemical compound and which I have discovered will discharge to a pure white or natural silk color by ordinary discharge printing methods known to the trade.

Operation C It is to be noted that additional loading may be had at this point by treatment with lead acetate or lead nitrate. Operation C therefore is only plausible where additional weight is desired in cases where the motif of the discharge printing does not require white or natural silk color. Therefore Operation C is an alternative operation, for the only reason that lead salts are here substituted is because of the economy of carrying out the process. Where desirable Operation C may be entirely eliminated.

Bearing, the preceding remarks in mind, the resulting silk from Operation B is treated with soluble lead salts, either lead acetate or lead nitrate for thirty-five minutes at 125 F. in a 2 Baum solution.

After the soluble lead salt treatment the silk is rinsed in a cold, then a hot, and then another cold water bath in successive steps to remove the excess lead salts. Following the rinsing operation it is necessary to render the lead salts insoluble by treating the silk with a cold solution of disodium phosphate of 2% concentration. The percentage here is by weight. A 2% solution of acetic acid would be ten pounds of acid to 500 pounds of silk. Then to remove excess di-sodium phosphate the silk is subjected to rinsings of cold, hot and then cold water.

Operation D Whether or not the fabric is treated with the lead salts of Operation C, it is necessary to sub ject the silk to this treatment of Operation D. This operation consists of using sodium silicate, sodium aluminate, or aluminum sulphate for the adding weight and sealing the previous weighting agents to the silk. This treatment has given satisfactory results when used with either of the foregoing solutions when worked at approximately 130 F. for a period of twenty-five minutes. Depending upon the amount of weighting compounds used in the preceding operations, the invention gives satisfactory results with these solutions ranging from to 2 Baum. Thereafter, the silk is rinsed in hot and cold water as a final step in the process.

Having thus described my process what I claim as new is:-

The process of weighting silk comprising subjecting de-gummed natural silk to an initial tin phosphate treatment consisting of the successive steps of immersing the natural silk in stannic chloride, hydrolizing the stannic chloride impregnation, treating the silk with di-sodium phosphate, and removing the excess di-sodium phosphate by washing; then repeating the tin phosphate treatment no less than two times; then washing the tin phosphated silk with acetic acid solution; then treating the silk with zinc acetate followed by washing; thereafter treating the silk with di-sodium phosphate thereby impregnating the silk fiber with a compound zinc-stannophosphate; and thereafter treating the resulting product with sodium silicate to form the final product.

FREDERICK W. MILLER. 

